At present, liquid crystal display devices are widely used in various electronic devices, such as computer monitors, TVs, notebooks, mobile phones and digital cameras, due to their advantages, such as slim shape, energy saving and low radiation.
Referring to FIG. 1, a circuit diagram of a typical liquid crystal display device 10 is shown. The liquid crystal display device 10 includes a liquid crystal panel 11, a scanning voltage generator 12, a scanning driver 13, a data driver 14 and a common voltage generator 15. The scanning driver 13 and the data driver 14 are configured for driving the liquid crystal panel 11. The common voltage generator 15 is configured for providing a common voltage VCOM to the liquid crystal panel 11. The scanning voltage generator 12 is configured for providing a first scanning voltage VGL and a second scanning voltage VGH to the scanning driver 13.
The liquid crystal panel 11 includes a plurality of parallel scanning lines 131, and a plurality of parallel data lines 141 orthogonal to and isolated from the scanning lines 131. The scanning lines 131 and the data lines 141 are configured for defining a plurality of pixel regions 102. Each pixel region 102 includes a thin-film transistor (TFT) 103 arranged in a vicinity of an intersecting point of the scanning lines 131 and the data lines 141, a liquid crystal capacitor 104 and a storage capacitor 105.
The liquid crystal capacitor 104 includes a pixel electrode 1041, a common electrode 1042 and a liquid crystal layer (not shown) sandwiched between the pixel electrode 1041 and the common electrode 1042. The storage capacitor 105 includes the pixel electrode 1041, a storage electrode 1051 and an insulating layer (not shown) sandwiched between the pixel electrode 1041 and the storage electrode 1051.
The thin-film transistor 103 includes a gate electrode (not labeled) connected to one of the scanning lines 131, a source electrode (not labeled) connected to one of the data lines 141 and a drain electrode (not labeled) connected to the pixel electrode 1041.
The scanning voltage generator 12 is configured for providing the first scanning voltage VGL and the second scanning voltage VGH to the scanning driver 13. The scanning driver 13 is configured for providing a plurality of scanning signals to each scanning line 131 successively according to the first scanning voltage VGL and the second scanning voltage VGH. When the scanning driver 13 provides the scanning signal to one of the scanning lines 131 connected to the thin-film transistor 103 according to the second scanning voltage VGH, the thin-film transistor 103 is conducted. The data driver 14 is configured for providing a plurality of grayscale voltages to the plurality of data lines 141 so that one of the grayscale voltages may be provided to the pixel electrode 1041 via the source electrode and the drain electrode of the conducted thin-film transistor 103.
The common voltage VCOM generated by the common voltage generator 15 is provided to the common electrode 1042 and the storage electrode 1051, respectively. When one of the grayscale voltages is provided to the pixel electrode 1041 via the source electrode and the drain electrode of the conducted thin-film transistor 103, a voltage difference is generated by the common voltage VCOM and the grayscale voltage between the pixel electrode 1041 and the common electrode 1042 of the liquid crystal capacitor 104. Liquid crystal molecules in the liquid crystal layer sandwiched between the pixel electrode 1041 and the common electrode 1042 may be induced to a predetermined angle in order to achieve a predetermined gray-level according to the angle of the liquid crystal molecules. The storage capacitor 105 is configured for maintaining the grayscale voltage on the pixel electrode 1041, so that the grayscale voltage on the pixel electrode 1041 may be maintained until a successive grayscale voltage is provided to the pixel electrode 1041.
In general, there is a parasitic capacitor 106 between the gate electrode and the drain electrode of the thin-film transistor 103. When the voltage on the gate electrode of the thin-film transistor 103 changes, for example from the second scanning voltage VGH to the first scanning voltage VGL, the voltage on the pixel electrode 1041 changes correspondingly, because the voltage difference on the parasitic capacitor 106 cannot change instantly. Furthermore, the common voltages VCOM on the storage electrode 1051 and the common electrode 1042 changes correspondingly, because the voltage differences on the storage capacitor 105 and the liquid crystal capacitor 104 cannot change instantly. Therefore, a picture displayed on the liquid crystal panel 11 may flicker due to the changes of the common voltages VCOM on the storage electrode 1051 and the common electrode 1042.
What is needed, therefore, is a liquid crystal display device and a method for driving the liquid crystal display device which may overcome above problems.